Recently, I have written a few things about Agile methods and Scrum. I feel that they are not the solution to everything, because in certain scenarios they have severe risks and drawbacks. I warned about how certain (sub-)problems cannot easily be solved in an iterative fashion, and require proper thinking, design and perhaps even prototyping before you move into Scrum.

Now, I have been reading the book “Requirements Engineering” by Axel van Lamsweerde. I did not expect the topic to pop up, but there it was. And in retrospect, it makes sense: requirements engineering is very closely related to the problem I was describing. You would not generally take a Scrum-approach, but you’d rather have a more spiral approach, where you refine your results in ever larger iterations (much like how you would first develop a prototype with a small team, and then refine it to the end-product with a larger team).

Van Lamsweerde does one better than that, however. He specifically goes into Agile development and points out that Agile methods only work under specific assumptions. In other words: they should only be applied in specific scenarios, and are not the solution to everything. He lists the following assumptions:

All stakeholder roles, including the customer and user roles, can be reduced to a single role.

The project is small enough to assign to a single small-size team on a single location

The user is available for prompt and efficient interaction.

The project is simple and non-critical enough to give little or no consideration to non-functional aspects, environmental assumptions, underlying objectives, alternative options and risks.

The user can provide functional increments quickly, consistently (so that no conflict management is required) and gradually from essential to less important requirements (so that no prioritization is required).

The project requires little documentation for work coordination and subsequent product maintenance. Precise requirement specification before coding is not an issue.

Requirements verification before coding is less important than early release.

New or changing requirements are not likely to require major code refactoring and rewrite, and it is likely that the people who develop the product, will also maintain it.

He specifically points out that mission-critical software is one area where agility is a poor fit. He also points out that ‘agility is not a binary notion’: For each phase of the project, you can choose to use less or more agility, depending on what is required for that phase. I think this is quite interesting, because Scrum-consultants seem to claim the exact opposite: any derivation from the strict rules of Scrum is considered a ‘Scrumbut’, and they always advise to apply Scrum more strictly.

Now, getting back to the example I gave earlier, where the team developed a system based on queues, where they should have used a database… Quite a few of the 8 above assumptions did not apply in that scenario, so Scrum was a poor choice from the start. The queues-vs-databases example itself immediately points to a violation of assumption 8: major code refactoring was required because of the ‘new’ requirements for prioritizing. But also, the project was a very mission-critical project for the customer. It was also a fixed-price, fixed-deadline project. This would violate assumption 4. The customer was in another country, so 3 did not apply either. I would also say that at least assumptions 1 and 6 were violated as well.

When I first heard of Agile and Scrum, it was mostly related to web-application development. And in retrospect, this makes sense. I suppose (small) web-applications tend to be a reasonable fit for Scrum. However, as we also discussed in the comments of the earlier articles, there are also projects that are highly technical and experimental in nature, and they are a very poor fit for Scrum. A spiral-like approach is much more natural there, where one or two people start by collecting the requirements, and iteratively working out the risks and problematic areas, perhaps developing some proof-of-concepts/prototypes during that time, and then refine the requirements, design etc, so that the project will gradually mature, and it starts making sense to add more people to the project, because there are now reasonably well-defined goals and workloads to be distributed.

The irony of it all, is that Scrum never claimed to be the solution to everything. Take the original paper by Ken Schwaber: Figure 6 clearly shows the Scrum Methodology, defining 3 different phases:

Planning & System Architecture (Pregame)

Sprints (Game)

Closure (Postgame)

The way phase 1 and 3 are drawn in the figure, show that they are not really part of what Scrum is about (the sprints). They are shown in a way similar to the Waterfall methodology in Figure 1.

Schwaber further remarks:

The first and last phases (Planning and Closure) consist of defined processes, where all processes, inputs and outputs are well defined. The knowledge of how to do these processes is explicit. The flow is linear, with some iterations in the planning phase.

So basically Scrum never meant to solve everything with sprints. Not the planning, not the (intial) requirements, and not the system architecture. For some reason, everyone seems to have forgotten about this, and thinks Scrum is about doing everything in sprints, even all the design. That is a recipe for disaster with any non-trivial project.

2 Responses to Read any good books lately?

I found your work at oldschool section “stable raster” some nice raster with soft scroll and music.
I am back to my old c64 after thirty years and I will try to make some intro.
So I need help with code or some examples